The infamous “god of chaos” asteroid poses less of a risk than we thought, experts have said.
The asteroid is regularly at the centre of scare stories because it was considered to have a small chance of colliding with the Earth. That meant it was placed on the European Space Agency’s “Risk List”, and the subject of detailed observations.
Apophis – named after the Egyptian deity, or “lord of chaos” – was first detected in 2004, and soon after that researchers suggested it could hit the Earth in 2029 and 2036. Further research ruled out those impacts, lessening the concern.
But experts remained worried about a potentially collision in 2068. In part because of the asteroid’s grand name, as well as its potential danger, it became infamous and regularly written about as a potential danger that could strike the planet later this century.
The asteroid made a relatively close approach earlier this month, however, when astronomers had the chance to scan it with Nasa equipment. That gave them a better view of the asteroid’s orbit, and allowed them to be confident in ruling out that it could impact any time in the next century.
Apophis will fly past Earth in 2029, passing by at a distance of less than 35,000 kilometres and so close that it will be visible with the naked eye. That close approach was one reason scientists worried about the flyby latest this year: coming so close to Earth means that it could be affected by our gravity, and it was difficult for researchers to know how that might change its trajectory.
If the asteroid were to pas through the dangerous “gravitational keyhole” on that 2029 visit, then it might find itself on a journey that would take it towards a collision in 2069. The new data allowed scientists to have a much more accurate picture of its trajectory for 2029, however – narrowing down the window of possibilities and allowing them to be sure it would not pass through that all-important keyhole.
“A 2068 impact is not in the realm of possibility anymore, and our calculations don’t show any impact risk for at least the next 100 years,” said Davide Farnocchia of Nasa’s Center for Near-Earth Object Studies (CNEOS), in a statement.
“With the support of recent optical observations and additional radar observations, the uncertainty in Apophis’ orbit has collapsed from hundreds of kilometers to just a handful of kilometers when projected to 2029. This greatly improved knowledge of its position in 2029 provides more certainty of its future motion, so we can now remove Apophis from the risk list.”
Having a place on the risk list does not necessarily mean that an asteroid poses a significant threat. An object only needs to have a non-zero chance of hitting Earth.
If an asteroid is placed on the list, researchers continue to better understand its orbit and whether it might bring it into collision with our planet in the next 100 years. If astronomers can then be sure that it does not pose any threat, it is taken back off the list.
Apophis refused to leave that list, however, and evaded scientists’ attempts to gain evidence that it would not crash into our planet. As it stuck around, fears about the “god of chaos” grew – but can now be put to rest.
“The discovery of Apophis and early work done to track and understand its orbit, occurred when today’s planetary defence activities were still in their infancy,” said Juan Luis Cano from ESA’s Near-Earth Object Coordination Centre in a statement.
“That this happened at such an early period in the discipline served as strong motivation to improve our capabilities to accurately predict the motion of these interesting and potentially dangerous objects. With today’s removal of Apophis from the Risk List, we are closing a very enlightening chapter in the history of planetary defence”.
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